It is not safe to run just lap belts on a child seat.
Look at Wesco Performance they sell a good hardness for a great price. This is the direction I went for my 3 year old. It makes me feel good.
I ordered standard lap belts in black but I will put in 2 "D" rings on the pass. rear floor side for the Child Seat as anchors. I got gran kiddies I want to hual around.