Which Vertical Knee Raise (VKR) / Power Tower should I buy?

Hi. I am looking for a small VKR or power tower that is suitable for a shorter person (5'4" - 5'9"). I used one in a gym a long time ago, so I am pretty sure they exist. My biggest issue with the ones I have seen in the stores so far is that the forearm pads for the VKR position are just too far apart. I am looking for something that will allow me to have my elbows no more than 18-20 inches apart. Does anyone have any recommendations for specific models? I am not looking for a fancy setup - being able to do just knee raises and pull ups on a stand alone piece of equipment would be fantastic. Thanks!