I agree with slowcoach, Blea Water would be nice place to camp - right at the end of valley and surrounded by steep slopes. Good description too. Head down the ridge towards Rough Crag (go steady as its steep in places but the exposure is minimal) when it flatten outs before what would be a short climb up to Rough Crag head south down to the eastern corner of Blea Water. I don't think OS maps show a path here but it fine.
Another alternative would be camping in valley of Riggindale Beck, up to you how you get here. You could descend Kidsty Pike and turn back on yourself up along the beck, or head across Rough Crag and descend (north) whenever it looks okay.
I don't recall anywhere being that boggy, even if it is with a little tent you'll find somewhere to pitch and if you can't you're doing something seriously wrong
