Your profile pic says San Juan 21 but that looks exactly like my Hunter 26 set up. I've done this twice. When I got mine, the plastic divider was also broken. I called the SBO store... they could not find the part either but they had one made for me. Won't swear to it but I think they only charged me $18. I had to drill my own hole in the card for the pin.
Anyway you are in luck-ish...
1) SBO might make you one or maybe when they made mine, they went ahead and made a few more out of the same scrap piece of plastic... but if not it is not much more than a plastic credit card cut to the right shape. So if you can locate a sturdy piece of heavy-ish plastic and cut it to the right shape, you are good to go. An old I.D. card would work perfectly.
2) The pin is held in with 4200 and not 5200. Get a plier similar to this...
I had Crazy Dave there to help me the first time... SO!... Here is what you do.... grab the pin between the sheaves and start to pry it a little at a time out of the hole. Once you get enough of the pin out of the hole to grab it with vice grips... you are almost home. It eventually comes out.
Clean everything off and fit your credit card in the right place. Put a dab of paint (I used white-out) on the pin and insert it back in until it touches the credit card and marks the location for the hole in your credit card. Set the card on a block of scrap wood and get the right size drill bit to make a snug hole. Dab some 4200 in the pin's receptical hole being careful not to get it on the pin and put it all back in place.
BTW: The one I bought from SBO lasted only two seasons before the UV did it in. The second one I made out of a resin squeegee card... similar to this....
So... If you want to try it on the cheap...I'd suggest you just go through the dresser drawer looking for an old gym I.D. card or something similar and cut it to the right size. You can always paint it with some krylon plastic paint if you want it to look right. Or go to auto zone and buy a resin squeegee.