Tamiya makes a german mounted cav set that has the saddlebags mounted to the front of the saddle. The kit is cheap enough that it would be worth it to pick it up if you wanted to save yourself the time of scratchbuilding them.
The references I have show the Pannier containers as being a little deeper and wider than the cav saddlebags but I suppose there is no hard and fast rule. In the field you could use what ever works I suppose. There are some photos of the classic looking rectangular saddlebags on the Waffen SS cav units that look similar to the pannier containers but not as wide. There are plenty of photo references though of just about anything and anything being used on the bikes to help haul gear.
The simple shape of them should make them easy to scratchbuild.
Mike
"Imagination is the dye that colors our lives"
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