I'm building a 1/32 Storch at the moment, and had a wander round the hobby shop having a look at all the extra bits you can get for 1/35 scale armour with both sides and a range of other sides gear available. There were fuel cans, mechanics toolboxes and workbenches, blankets and tarps, trailers full of ammunition for a range of guns, water bottles, and anti-tank things. There was even a kit with two donkeys and their German handlers! There was a flat tyre kit including the flat tyre, a brake drum to put on the model axle, and jack for a VW! You were supposed to buy the matching VW kit, but it looked like a schwimwagon (spelling?) kit would do as well. That could be fun to weather and put into a diorama considering my (and most other old soldiers!) love of doing donuts in the paddock when it rains!
Those old Volkswagens were extremely hard to bog and will get through almost any wet paddock, leaving a great track! And from experience at home on my farm, most dual wheel trucks will also spin real well and do some pretty mean circle work!
As well as all the bits like this, many of the things you would see tied to the side of a tank would be readily made from a range of "craft" or household items. The foil liner from a cigarette packet can give a heavy canvas look if painted and can be rolled easily. Even thin lacy materials can be made into camouflage nets with a few cuts and extras.
Hope this helps, Peter