The main problem with regard to Peter Pan merchandise, outside of Disney, is that there isn't just one representation of the characters. As it started as a play with different actors and costumes every few years, and the first illustrated edition coming out a few years later, there never was one depiction that made its mark (unlike say, Winnie the Pooh as illustrated by E H Shepard which established the characters from first day of publication). So the depictions changed over the years according to design and propriety trends - for instance, Peter's costume changed from the full red suit complete with jerkin, shirt, leggings to a green skimpy leafy costume, or a pseudo-Robin Hood attire.
There was some merchandise based on Frampton's statue in Kensington Gardens in the 1920s, but after the copyright went to GOSH, there wasn't so much as it wasn't a priority for them (especially after the hospital was incorporated into the NHS), apart from the Peter Pan League created in 1930 with a logo designed by EH Shepard himself. GOSH's hospital shop and mail order shop does offer some Peter Pan items but in a limited way. It is now complicated by the fact that Disney owns most of the trademarks in the characters, so other would-be merchandisers wouldn't be able to produce stuff based on a different design.
I have seen quite a few Disney things such as mugs, snow globes, etc on eBay but suspect there will be more Disney merchandise coming out when their new film is released.