Hi Michael,
I’ve had a look but I can’t see anything obvious. The problem is that no buses from Hammersmith go very far in the direction of Croydon, so your last leg will always be relatively short.
The best I can suggest is walking as far towards Wimbledon as you feel able, then touch in at the tram stop as the tram arrives and hope you get lucky. Bear in mind that if you do the journey both ways then the most you’ll be charged is 3 buses, as that is the daily bus/tram cap (£5.25). If you’ve made any other train journeys earlier in the day then they also count towards whatever rail cap you reach.