Onsen that allows tattoo's in Tokyo

Well 2 weeks tomorrow I will be in Tokyo, I know of one onsen in Asakusa that is fine with tattoo's, but want to hedge my bets and make sure there's more than one on my list.

Anyone know of any tattoo'd gaijin friendly onsen in the usual generic places in Tokyo?

Going for a 6 hour session at the tattooist on Saturday, so will most likely have some sizeable tattoo's on my trunk before I arrive in Japan.

I don't mind if it's sleazy or full of Yak's, just want somewhere to have a soak in the evening.

Thanks in advance.