Spectrum 2-8-0 tender coupler conversion

[cmsluss]

I bought a first run n scale Spectrum 2-8-0 Consolidation... manufactured about 10 years ago.  I tried swapping the rapido coupler on the tender with the Bachmann PN-9722 knuckle coupler that is packed with some Bachmann n scale rolling stock.    Using the engine to pull passenger coaches that have Micro-Trains knuckle couplers... the tender doesn't stay coupled to the train.   

I'd prefer not to drill a hole in the tender to install a knuckle coupler.  What is the next best coupler conversion for the Spectrum 2-8-0? 

Thanks much!

[TJ]

 May I suggest MT 1128-1130's I found that 1128-1129 worked the best for this conversion.

MT 1128-1130's Are now
 
MT 00130012
MT 00130013
 MT 00130014

Unless you want to use a 4-8-2 tender which has a knuckle coupler and swap out the tender trucks.

T.J