Two thoughts, and I wish I had seen this before you ordered boards.
First, you might email your supplier of SCA to 50 pin adapters and ask him if he can get the components unassembled. You need everything except the circuit board anyway, and it should save him money with his supplier if they just ship the unassembled components.
I don't know if their flow will allow that to work, but it is another avenue, in case you can't get to a SCA connector manufacturer, or in case they want too much volume.
Second, would you mind explaining your termination scheme? It looks to me like you're tieing Term. Pwr. to the signal lines through 110 ohm resistors with a couple of diodes in the line to step down the voltage. I see what you're trying to do, but it is not going to be reliable. According to the literature, you can't count on Term. Pwr. being a reliable 5V. Plus, your voltage seen at the signal pin isn't constant because it depends on the current that flows through the single resistor -- no connection to ground, and that will change as the signal switches between 0 and 1. I'm willing to believe that I've overlooked some trick of electronics that makes this a reliable termination method, but it looks like a contraption for wildly varying termination current/impedance to me.
If one is going to tie the signal pins to Term. Pwr through 110 ohms of resistance, then the Term. Pwr. needs to be a voltage regulated source of 2.85V. This is active termination and it requires an actual voltage regulator in the circuit, such as an LT1086CT.
If you're not going to use a voltage regulator, then the old method of passive termination is to tie the signal pins to ground through 330 ohms and to Term. Pwr. through 220 ohms. This still has the problem that Term. Pwr. may not actually be 5V, but it has the virtue that the voltage at the signal pin is constant because of the voltage divider created between Term. Pwr and ground.
