You should be able to run a 1gb PIII flip chip if your got a slot key adaptor but you won't be able to overclock this one if your limited to 133fsb.
Otherwise your other choice would be a PIII 1000E slot1 100fsb cpu(harder to find), then your got a good chance of hitting anywhere upto 1333mhz. Both these cpu's are still expensive but you might find one cheap enough somewhere.
Lasty and most likely could be the best way, get an upgradeware (http://www.upgradeware.com) adaptor and fit a tualatin celeron to it, get either a 1.0a or 1.1a.
1.0a x 133fsb = 1333mhz (next to no risk reaching this speed
1.1a x 133fsb = 1463mhz (more of a risk but easy obtainable)
1.2a x 133fsb = 1596mhz (you most likely won't reach this speed unless your lucky with a newer stepping cpu or have good cooling plus voltage tweak)
If you want to take no risk then get a 1.4a celeron and run it at stock fsb or slighty over.
Tualatin celerons are almost as good as coppermine PIII cpu's clock for clock, but the coppermine with never clock as high as the .13micron process celeron.
Im almost certain it will work. I used one of their 370GU adaptors with my BX133RAID and a SA6R I use to have, both worked fine. Only problem I had was the voltage would reset itself to default if I was to power down the system. Both boards were on their way out due to bad caps on many old abit boards, so you might wanna check them out to see it yours are still ok. i fixed the SA6R and it ran mint after that. by that time i got a tualatin board, the one in my sig. don't doubt these type celerons, these things can fly for what they.
Slot-T adaptor should act differently and looks to me in the picture as more as a full unit when compared to the 370GU. Says it has on board voltage tweaking all the way upto 2.05v!
Their webpage lists your board as compatiable: http://www.upgradeware.com/english/product/slott/compatibility.htm