Ankle weights will work. I've done then it that way. A weight belt works too. A weight at the hips is less leverage that one at the ankles so it will feel different and likely require more weight to get the same effect. You may need a weight belt for dips and chin ups at some point, but I wouldn't worry about it for leg raises.
Good to hear! What’s a good volume if I want to pack some lean meat in that area? 4x10 or is that too much?
I used to work core 9x15 using 3 different variations interspersed with other exercises. You know, one of those "volume" myths...