From what Ive gathered is that a 1 Meg pot is called for...and Justin's site is recommending a 250k audio taper pot...and I kinda get the impression thats because thats all anybody could find.
But I think Ive found a dirrect replacement, although I havent tried it yet, follow me and tell me if Im on the right track here.
http://www.angela.com/catalog/guitar-amp-parts/FENDER_AMP_PARTS.html
Heres another source for the same pot/part with a pic for visual confirmation
http://www.darrenriley.com/shop/cart.php?m=product_detail&p=1327
Looks like the correct part to me, took me a lil while to find it, but am scratching my head why nobody else ever found this...it seems the old info on the Hotrod pages might need an update.