486 Overdrive CPU source?

I have a Dell Precision 486/33S computer. Has only 28MB of RAM but a 1.2GB
drive. As you may notice from the name it is a 33mhz 486SX (no math
co-processor). I want to turn this into a usable workstation for internet
and basic word processing. It works now but it would be better if it was
faster (duh).

Anybody know where I can get an Overdrive CPU to pop into the empty PGA
socket on the mother board?

Alan