Bean bag idea...

[Theisey]

Oh my, what next Mike, different colored flags for 5 vs 10 vs 15 yard fouls? Only the NFL uses blue bags.
No need to complicate things.. Just drop a (white) bag at every end-of-kick spot.

Personally speaking, you might consider having three bags if you are a downfield official. Two in your belt and one in your hand on kick play downs.

Why? consider this, a kicked ball is rolling around, touched by K, picked up by R who fumbles when hit a few yards later.
Third bag is in the pocket until a kick down is about to go off. At that time it's in your hand.
May only happened once in your lifetime or not at all, but you'll be prepared.
Think of that great observers rating you'll get too!