Is is feasible for you to trim your back to common specs? Wooden holders don't have static electricity issues like plastic ones can have and they're not as modern-looking but I'm not trying to impress anyone. I got mine for $9 each shipped. I can't find plastic ones for less than $30 each and those are so cosmetically worn that appearance is no longer an issue vs. wooden ones. I can't find really nice modern plastic 8x10 holders for less than about $50 each. Of course, your choice hinges on how important price is to you. If price was of small concern to me I'd just buy the best and be happy that I could do so.
There are longer wooden holders, BTW, that are the same length as longer plastic ones. Fidelity with metal tops come to mind.