Niklas,try the Aero Vodochody L-29 Delfin they look simular in design..Since the paper line drawing looks close I'm not sure about the guns or the cockpit shown as a single seat the Delfin is twin. Perhaps you want to look into a few other Russan A/C..saw somewhere that Yak lost the orginal contract to the Aero...I thinkt he model was a Yak-90 though I can't find a photo.
I hope this helps