I assume ya mean single unit... (for the older Tamiya's)

Tower Hobbies has a few, but you want one ~with~ reverse:

[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXAMN7&P=7]DuraTrax Sprint - 29.99[/link]

[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXGMR5&P=7]Tamiya TEU 101BK (bulk) - 37.99[/link]

[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXGZX1&P=7]DuraTrax IntelliSpeed Auto-Sport - 37.99[/link]

[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXATE3&P=7]Airtronics BL-Racer - 39.99 USD[/link]

[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXJM28&P=7]Traxxas XL-1 - 39.99[/link]

If you want a double ESC unit (for the later DMD tanks):

[link=http://www.dimensionengineering.com/Sabertooth2X10RC.htm]Dimension Engineering 2x10 RC - 64.99 US[/link]

Thats the NEW options... any older eBay-sourced buggy/monster ESC that has reverse should be ok as well. I've got a few old Futaba 112's & 210's I intend to recycle as tank controllers.

Psst: He said ~reliable~, HL's ain't unless used carefully or modified (see assorted comments about burnouts)