If there's one new periferal for the Amiga 500 I can recommend without hesitation it's the ACA500+ from Individual Computers. Among the specifications is 8MB RAM, 2 Compact Flash connectors and a few expansion ports. One can be used to connect a Amiga 1200 expansion, e.g. an accelerator card. I have connected a Blizzard 1230 IV and it works like a charm. Price is € 135,00 which I think is very affordable; bang for the bucks!
But... Individual Computers does not recommend this setup. Use in an A1000 is not supported and could damage the ACA500+. You've been warned!