Amigakit.
Or if you're after NG Amiga stuff, try Acube directly. If interested, x000 stuff through A-EON and their retail partners. Amigakit has lots of legacy Amiga stuff, as well as a good NG selection. For things like FPGA solutions or newer accelerators like the Vampie, Google is your friend. Not hard to find.
Not hard to find. The largest Amiga around reseller (by proxy - A-EON owns Amiga.org, and Amigakit are tied in with them in some capacity) owns these forums, after all.