The 70 is in stock here: http://www.jr.com/JRProductPage.process?Product=3964406
It's a good place and I've bought from them in the past. It looks like they are currently out of stock of the 55, but if you call and ask, they might have an ETA.
BTW: I have heard the 70 has the amp section from the 50 and that the 55 has a newer amp section. There is also a new model coming out in July, IIRC.