I'm about to buy my daughter a pair of gerbils. I thought it would be a good idea to get a playpen for them so that she can get them out without losing them. However, having looked at products commonly available (eg Joy Rodent enclosure), all the reviews say that the gerbils (and hamsters) just climb out immediately! Has anyone got any recommendations for playpens (indoor, not too big) that actually work?! We wouldn't leave them in there unsupervised, but it would be good if we can find something that they don't spend their whole time escaping from......!