EDIT: Hamfist- out of interest- what pedal(s) are you using now if any?
I have a Blackstone Appliances Mosfet Overdrive (amazing pedal !!) and a CMATMODS Brownie for use into a clean amp. Although I haven't had a chance to try them into a driven amp yet, as both the pedals are fairly new, and I'm still awaiting delivery of my Ceriatone 2204.
Recently, I had been using an MI Audio Blue Boy Deluxe and an SPF Ego Booster into a dirty amp. Both pedals, I would highly recommend.
The BBD is a highly tweakable TS-9 like pedal, which can range from clean boost thought to extra overdrive, with all sorts of EQ options (having 4 EQ knobs). You don't have to have the mid-hump, bass loss of a TS-9, that's for sure. It can take a while to dial it in, but it is very versatile. This pedal has worked well with every dirty amp I have ever used it with. It sounds truly horrible into a clean amp though !
The Ego Booster is a very nice Clean Boost, with options to use it as a treble or bass boost instead.
Both pedals should be easily available.