Got to looking around after sending the above Post Reply.
This might be of some assistance in what you're looking for.
Price is reasonable. I'd not hesitate to use them if needed a scope mount.
Of course you'll have to drill n' tape the back/side of the action, and front ring.
For a collector that will cause them to cringe n' bring tears to their eyes!

No idea what the condition of your Model 1903 is in, but it's your call what you want to do with it.
They're tools, first and foremost...

Hope it's ok to post the web address here for you:
http://www.gunbroker.com/Auction/ViewItem.aspx?Item=415695480

I never really was a collector, but use to have GAS (Gear Acquisition Syndrome) with Mannlicher Schoenauers: MCA's in .243, .308, .30-06. 6.5x54, 7x57 and even the rare .358, all full stock carbines. A Model 1952 in 9.3x62, along with assorted Model 1903's. Was one of the founders of the Mannlicher Collector's Association when it started in 1985. In the 1990's thinned the herd down to my favorites, keeping 3 Model 1903's. Still have them to this day, along with an MCA in .308 and an MCA in .264. I'd sold the MCA .308 in 1994 in Alaska, then of all things saw it on an auction site last year and bought it back - 19 years later!

It seems once the Mannlicher Schoenauer's get in your blood, they never truly go away...!