I did a quick check, and looks like the European 444 used the BC-144 gas engine. Open this link to go to the Case/IH online parts store:
Official Case IH Online Parts Store and Case IH Catalog for Best Parts Search and Best Parts Look Up. Case IH Parts for Case IH Tractors, Case IH Combines, Case IH Tractors, Case IH Manuals, Case IH Parts I've already got it to the BC-144 engine catalog, and have it on the cylinder head page. Look for #'s 24 & 25, for intake and exhaust valves. Click on each item, and it will open to another page, where you can copy and paste the part number to a search engine, if you want to do some online shopping. Messicks here in the U.S. shows the intake to be &35.97 U.S., ea., and the exhaust to be$46.66 U.S. each. Maybe you can find a better deal elsewhere. At least you have some part numbers to work with. No where did I see, in just a quick search, a complete set.
Just make sure that engine is the BC-144. Hope this helps... Good luck..!!