I built a custom aluminum bolt a couple years ago but it was a trial and error fit.  It worked out and has been working fantastic.  When I built the 1925 I used that bolt body to install the 25 caliber probe I made.  I want to make more aluminum bolt assemblies but wanted technical drawings so I designed the bolt from my old drawings and measuring a factory bolt.  To make sure it worked before cutting it from aluminum I 3D printed it to verify the design.  The printed bolt assembly works very well.  It works so good I will print more to use until I get around to machining them.   The original aluminum version used a spring that was not contained to actuate the bolt handle.  That proved to be a pain when installing in the receiver.  I wanted to use a plunger and captured spring in this design so assembly into the receiver would be as easy as the factory bolt.  I machined the plunger on the lathe but it could also be made using a file and power drill.  Using 3mm brass rod the rod can be chucked and spun against the file to reduce the end to the 2mm dimension.  It can then be cut off with a hack saw and filed to length.  The probe is best made using a lathe.    I have uploaded the models to Thingiverse.

Even if you don't have access to a 3D printer you can order parts from printing services such as CraftCloud