You could buy an 8mb fast ram card with fpu from ebay or something, but they tend to be just as expensive as a the ACA1220. If you do go that route, double check there's an fpu and oscillator installed as those types of cards usually sold without fpu. It's going to be slow though, but if speed is not an issue then that's nice for you. People are so impatient these days.
Also, you can't use the pcmcia card slot without jumpering the ram to 4mb on the trapdoor card. This isn't an issue on real accelerator cards (with cpu, such as any of the Blizzards/Apollo's/ACA etc.).