If you can find a used Anatek SMP-7, that is a good one: it has a MTC to SMPTE converter in/out as a bonus, and it may have a Mac interface, not sure \'cause I don\'t use MAC stuff.
If you only have Mac, read no further, tho there may soon be a Mac version.
To my surprise, Midi Over Lan (MOL) works very well if you are using computers for sample players. Most mobos have LAN these days and a hub costs very little, as do routers. If you also use Hubi Loopback (free) you can use the hardware midi ins & outs of all your computers. If, for example, you had 4 computers and you put midi cables on each of the game/midi ports, that would give you 64 midi in-out hardware midi channels, plus all the internal soft midi ports provided by MOL.