Many retailers, especially the smaller ones, are just hearing about this law now and the effect it could have on them personally or professional if they are found to be selling items out of compliancy. Just like here at ETSY some are very confused and to make sure their backside's covered they want proof that the items that they are caring are compliant even when the government has already exempted all the materials used in the final product. Perhaps sitting down with the store owner with the government issued documents in hand (or on a notebook computer) and discussing the law and it exemptioms and requirement in regards to your products specifically will ease their fears and allow you to keep your products in their shop as long as they know that all you really need is the proper labeling. Even if your able to prove to them that the products you are making are exempt from the lead testing the retailer can still under the CPSIA law can request that you provide them with a GCC as their proof of "due diligence" if they are ever questioned on the subject of your products. This link,
http://www.cpsc.gov/about/cpsia/faq/elecertfaq.pdf , will tell you what you need by law on your GCC.
If the retailer willing to read through the documents on items that are exempt from lead testing it will save you a whole lot of wasted money since from a quick look at your products it seem the caps & hats are made of entirerly exempt from testing materials. I suggest that you print this out
http://www.cpsc.gov/businfo/frnotices/fr09/leaddeterminationsfinalrule-draft.pdf highlight the passages concerning your raw materials to prove that the government already sees that certain raw components do not have levels of lead above their specifications and do not need further testing as long as they are combined with other exempted or tested below the limit components. If the retailer is unable to accept that as enough proof of the lack of lead in your raw materials then bill them the testing as part of their final invoice and let them go through the hassle of figuring out how much to add to each item.
If it's certifications on other testing like phthalates or durability & small parts or product specific CPSC regulations there are no exemptions from this if your products fall into areas that require these type of tests.
If you decide to have you items tested after completion you would have to contact some of the CPSIA approved labs to see if any of them will do the testing on small batch manufacturing, request quotes, and ask how many samples they need per batch lot. See
http://cpsc.gov/cgi-bin/labapplist.aspx for a list of approved labs. Lead testing can cost from $75 to $150 per individual base component used in the final product. So a final product that was made with 4 raw materials (ex. striped fabric, black fabric, red thread, and purple yarn) can run $300 to $600 plus the cost of the samples to get just the lead test results. The phthalate testing runs even higher about $350 to $500 for each part of the final product that needs testing. Testing costs for other types of tests, like use and abuse for small parts, vary widely and would be hard to know exactly what tests each final product would need without contacting the labs themselves.
The testing will only be good for items made from the same dye lot/batch # of raw materials. So say your able to get 10 hat from fabric with dye lot # 101 and 15 more from fabric with dye lot # 102 though you still used only a single spools of each color thread and 1 skien of yarn to complete all 25, samples from each dye lot of material will need to be tested seperately with tha above testing prices applying individually then certification written showing that both have their own set of test results.
Here's a link to the CPSIA's accredited labs
http://cpsc.gov/cgi-bin/labapplist.aspx . At the bottom is a way to narrow the search by the country the lab is located in and by what test you need done.