Kai Robinson (kr239) offers some RAM boards for Amiga 500 and more.
Check out his Github page here:
https://github.com/kr239
Tags / Projects:
A500-8MB-FastRAM 8MB FastRAM Board for the Amiga 500 & Amiga 500+
A500-DRAM-Board Allows you to replace A500 memory chips
A500-SRAM-Board Allows you to replace A500 memory chips
A500-14Mhz-Accelerator Bare-bones A500 accelerator + 8MB RAM