Boss SD-1 is a tubescreamer circuit with asymmetric clipping. Can get one used for $60 to $80. Very sweet sounding on a les paul with humbuckers. Slightly grittier than the tubescreamer 808 circuit which seem to work better on strats.
I A/B tested a SD-1 with a TS808 circuit before, they are very close. Just that the asymmetric clipping makes it slightly grittier. And it doesn't have as obvious a mid range hump.
The A/B test was conducted with a strat style guitar and a les paul. The TS808 sounded better on the strat and the SD-1 sounded better on the les paul. Do go and try out this pedal.