No, there are not. The GX-50 approach GPS does not slide into the enroute/terminal-only GX-55 tray. Only true slide-in replacement GPS upgrade I know is the Bendix-King KLN-94 sliding into the space formerly occupied by a BK KLN-89B. Next closest is the WAAS upgrade for the Garmin GNS430, but that requires antenna replacement.
Thankx for the feedback... I am using a mini iPad & WingX Pro. & planning on a ADS-B rcvr. too. I am strictly VFR & have been for 30 yrs. & almost 2000 hours, so maybe the monies would be better spent on.....? It's an Airplane.. There are lots of ways to spend.
Case Closed...?