I don't know if it's okay for me to post this link, if not admin just remove it, but here are the pads I get from Sam's:
  Sam's Club - Member's MarkŪ Comfort Shape? Underpads 
And it says they are 23" by 36" and $24.48 for a box of 120.  I'm telling you, they are the best buy out there if you use tinkle pads for your babies.  You definitely couldn't cut them because they are filled with some fluffy cottony type stuff that would spill out.  But you could just fold one end under to make them smaller/shorter. 
One pad does both of mine for a whole day.  They each pee on it about 2-3 times for a total of 5-6 pees, then I toss it and put out a fresh one the next morning.  I also keep one at the foot of the bed by their big-boy steps (what we call their doggie steps) and if they have to tinkle in the night they just go right down their steps to the pad, tinkle, then right back up to bed.