Looks like a 105 FC-5700 (10 speed) crankset in silver would be the matching crankset for that group, should be easy enough to find one NOS or used. I can't tell from the picture but that looks like the short cage RD so you will need to be mindful of the largest cassette cog restriction for the derailleur (going off of memory but if it is short cage you should be able to fit a 28t or maybe 30t largest cog).

That's a nice bike and deserves a crankset matching the rest of the components and optimized for the appropriate chain width. If in doubt, when you go to see it, count how many clicks you get from the right shift lever or get the part numbers off of the existing shifters and derailleurs so you can identify what generation of 105 you are looking at (if memory serves an "SS" rear derailleur is short cage and "GS" is long cage), but to my admittedly older eyes that looks like 5700/10 speed.