Elbow pads for striking are mostly there to lessen the chance of cuts. This way, a lot of the force in a hit can be dispersed over a large striking area instead of right at the point of the elbow. The cut generated by an elbow isn't like that of a knife. Actually, it is the skin on the person's head being compressed between two hard surfaces (the point of your elbow and their skull) and splitting open from the pressure. Instead of the pressure being concentrated on one point, it's spread out over the surface of the padding (which has much more give than the point of the elbow) and doesn't result in the type of cuts that would result as a by-product of a well placed elbow.
That aside (sorry for the rambling), you can get away with plain cloth elbow pads. These are the same you can get at your local sporting goods shop for volleyball or what not, but they have to be cloth
. The other types of elbow pads will have a hard plastic shell, which actually makes elbows strikes more lethal. So you wouldn't want to use elbow pads for skating or roller blading. Combat Sports (the MMA distibution side of Ringside) actually has their cloth Addidas Elbow pads
on sale for $4.95! Now, take in account shipping, and you might be better off making a trip to Big 5 or Sports Chalet.
The dedicated striking elbow pads are more like elbow sleeves with a full neoprene wrap. They offer a lot of support, and a layered cup of foam covered by synthetic leather for a striking surface. You can see what I'm talking about by clicking here
. They have them listed as sized "Regular" and "Large." You may want to call them up and ask if they will do well with you. If not, you may be able to get away with using Kneepads/Knee Sleeves in a small size like the Brute "Youth Predator Kneepad" (part #KPD07 - not listed on the website).
I hope that helps. If you're not sure on what will fit, call the place up and talk to customer service. Otherwise, just find a simple cloth pad that fits from a local store that will allow you to try it on and go from there!