The only L48 I've seen was in a display at a farm show and it had a set of 3-point arms stowed aboard in a bracket beneath the frame. Couple years ago, things may have changed.
Start by digging up a parts schematic at Kubota or Messicks or order one from your dealer and confirm for yourself the 3-point gear doesn't exist. To me, doesn't make sense, as the entire concept of the removeable backhoe is to use the 3-point. By the way, the machine has a PTO, doesn't it?
Now for the fun part: my bet is the 3-point assembly, complete, is unique to that machine and nothing else is going to fit. Just a guess, but based on experience with other orange iron.
IF you find a 3-point setup exists and IF you investigate pricing at a dealer using part numbers you've dug up, you'll find the entire lash-up will get close to $2,000. Maybe $1,600 on a good day. You can cut costs by obtaining pins, bolts, screws, maybe chains, odds-n-ends, at local hardware sellers (but get Gr-8 or better, not the buck-a-pound-on-sale stuff).
You can poke around used parts aka salvage or junque yards but, again my guess, parts (especially 3-points) are nonexistent. Experience here.
Please post back your continuing experiences so we may all learn.