That's a G3kA4. 12.7" barrel, using a HK33/HK-93 forearm, rather than the ~1.5" longer G3 forearm. To make it just like that, you'd have to SBR your HK-91 and send it to a smith to have the barrel and cocking tube cut down.
If you were just going for something similar to that, it wouldn't be too difficult.
The gripframe on that is a Navy-ish "0-1-20" version that would be pretty expensive. An alternative would be to buy a plastic SEF gripframe (~$35) and have it "clipped and pinned" for semi use. Standard SEF internals for a steel gripframe would work well with the plastic SEF gripframe, but you would have to buy the appropriate selector switch (~$25).
Pretty much all HK-91s had the black forearm, like in the picture.
The telescopic stock could be expensive if you insisted on Oberndorf Hk manufacture (~$400) or relatively inexpensive if licensed, but not Oberndorf stuff, was acceptable (
www.pof-usa.com for ~$200).
The paddle mag release seen on that G3 would have to be added to the receiver. It's well worth the ~$100 cost to install, but since it also requires a refinish, it would be best to do when doing other smithing jobs (like a G3k conversion). A less expensive alternative that requires no smithing is the Tac-Latch that many swear by.