[quote author="ian"]I couldn't find any bigger (let alone 15A and cheap) surface mount poly fuses on Mouser, neither could our sourcers in Shenzhen. We could explore through hole for a future version. If you a link to an alternate SMD part I'd be happy to check it out too.[/quote]
Digikey has a 3A 24V PTC fuse in SMD in stock, but I can't link to it since I have a new account.
Digikey P/N: MF-LSMF300/24X-2CT-ND
The through-hole stuff has somewhat higher holding currents, and a fair number are available if you're willing to drop the voltage spec from 18V to 16V, up to about 15A. MF-R1100, 16R1100GF, AHRF1500, etc.