I agree with HedgeHog. If your going for a 1 or 2 rep max once on a while, than maybe OK. But most guy's do not have a clue as to how to fit and wear a lifting belt anyway. Worn correctly(extra tight), the breathing is going to be limited, as is the circulation, to a degree. That's why only 1-3 reps max should be used for one set only. If you do buy a belt than it should be in person, rather than by mail order. Like buying a better quality shoe, try it on first. We have a couple of belts hanging on the gym wall for who ever wants to used one. Last time I looked, they were gathering dust.
Spending more serious time on strengthening the lower back and the abs will insure better core development. So as, you will have a natural strong and muscular "lifting belt" developed around the lower back. GoodMornings are on the top of my list. Can improve anyones squat and DL. Followed by SLDL's as a good second choice. Heavy ab work, not those marathon waste of time high rep workouts, can help balance out the strength of the lower back. Example: get in the ab crunch position and hold a 100lb BB above you. Now rep it out. Should get a feeling in the abs like never before. Good Luck.