30Thdiv,
Are you looking for a specific type of MG34 Feed-Tray........or just something to convert to fire the shorter 7.62x51mm Blanks (?).
As an alternative(s).........try asking the bigger Class-III Dealers such as Bob-Landies at Ohio-Ordnance-Works.........or Bob Naess over at Black-River-Militaria......etc..
Go over to the "reenacting-web-pages and post some WTB ads may turn up an MG34 Feed-Tray.
Last........if it is only going to be modified for shorter "Blanks"........have to looked at modifying an MG42 Feed-Tray (?).......
Regards, RichardS
US Army, RET
Blanksguy2001@outlook.com