I don't know regarding a silicone case that you can keep on during use. I use the sleeve case that Archos has available for the 7 Home Tablet (https://store.archos.com/cases-ci-27.html). It fits my 70 Internet Tablet 250GB model just fine.
It's for a different brand but it has similar size specs to the 70. the Cruz is 7.5"x5.6"x.6" .... and the Archos 70 250GB is 7.91"x4.49"x.55"... the 8GB model is: 7.91" x 4.49" x 0.43"
I'm betting that they made the above Cruz case just 1/2 inch bigger so it fits in easier... (fingers crossed)
I have the A70-250gb and bought the Tuff-Luv leather case. Model At the moment only the veggie version is available here.
This fits both the 8Gb and 250Gb version, but I had to modify the hole for the 3.5mm headphone socket (the case is cut for the 8Gb version). The case provides substantial, if slightly bulky, protection. The integral portrait stand works well, but the landscape stand not so good. When the device is hand held the top (or flap) folds back over the body of the case, behind the unit.
I also tried a foam (neoprene) pouch (from Hong Kong) and added a 0.5mm thick silicone foam covered alloy plate, for screen protection. This works, but the pouch is not a good fit. I can just get the Tuff-Luv case, with the A70, inside the pouch.