I might be the only appropriate person to respond, but my problem is opposite. Everything is too big for me! I really suggest you learn to sew, at least I had to. Otherwise I might be wearing high waters with flowers, duckies and monkeys on everything. LOL, sorry, its not cool lol..
If you dont want to do the work yourself, call wild bill and get pro-designed pads. He made some vert elbows to fit my super twiggy arms. Just be patient. On my other knee pads I use for my other sports, I had to double over the straps to shorten them. They havent come undone. Also if there is a hole where the strap comes out of, I double it up. So you could possibly just put a super long strap in there instead.
If you can sew, for you I would suggest taking out the stitching on the actual velcro, use heavy duty upholestery thread. Get some similar straps to the ones on the pads. Double them over and sew in at least 3 places. Would be cool if you had a sewing machine. Resew on the velcro pieces. They have these things to help take out the thread. Really try to learn this as otherwise you will always be dependent upon others to help you and wont have things that fit. I am much better sewing things to fit for ME then the pros are.