FWIW, here's a link to an inexpensive source for a 72-pin SODIMM which "half works" in my 510:
Current price for this 16-meg module is $2.99, but occasionally they drop it to $1.99. I say that it "half works" because no matter what combo of modules & settings I tried in my 32MB unit, I could only get the tablet to recognize an 8MB improvement. So, my Point 510 is sitting at 40MB right now. Still, 1.99/2.99 is "such a deal". Shipping was a reasonable $5.00, too.
While you're at this site, look around, as they have some good prices on systems.