Originally posted by phreon
Is it possible to source just the lithium battery tray from somewhere?
Frustrating, for sure.
I spent a bit of time searching online. Like you, I didn't discover any sources for the item by itself, for either the D-BG4 or D-BG5. BTW, it seems that Ricoh/Pentax calls it a "battery holder" according to the instruction booklet.
Concerning pricing, B&H carries a D-BH109 battery holder for USD $30. This item is not the one you're looking for, but gives a sense of the retail price for this type of replacement part. Incidentally, neither of the trays for my Pentax D-BG5 show part numbers on them.
The best I can suggest is a new DSTE D-BG5 clone (grip + both battery trays) on Amazon.com for USD $37. I would think that the plastic tray should be adequate, although it's not an OEM part. If it doesn't seem to fit or work in your Pentax grip, you could probably return the DSTE item to Amazon.
I know it sounds silly to buy a full grip set for just its plastic tray. However, if the tray is an essential part of your camera kit, it might be worth the cost. I don't know anything about the quality of the DSTE grip itself (or other clones).
Hope this helps.
- Craig