I think Victor, Bernzomatic, Harris, and Uniweld all make protable kits. If memory serves the last kit I saw (I think it was the Bernzomatic) came with a 20cf oxy tank like the one you mentioned.
If you're just going to use it sporadically it's probably okay. If you are getting it to do a lot of work it may not be enough. By "a lot" I mean using it on a daily or near-daily basis. I have a buddy in the HVAC business and he has a 20/10 setup. He uses it a good deal - at least two or three times a week from what he says - and I never hear him mention anything about it having too little gas.
Brad