I will be in Hamburg and Berlin in 2 weeks.

Would like to visit stores (preferrably near train stations for access purposes )carrying Marklin or other related Ho and digital supplies just for general interest and perhaps a small purchase.

Any advice would be appreciated.

Thanks

Diesel

hello diesel,
for hamburg i would suggest :
H.P.A. Schellhass GmbH , Lange Reihe 25, 20099 hamburg
Züge und mehr Modellbahnvertriebsgesellschaft mbH (1,2 km),altstädter str.17,20095 hamburg
märklin store, mönckebergstr.7, 20095 hamburg
all are within walking distance of the main station.
the maerklin store is not my favourite, but is is my personal point of view.
you can find all locations convenient by google.de subitem maps
there are more shops here in hamburg, some of them with a broad offering of 2nd hand items.
enjoy your trip