My first thought is do the pump makers provide any carry devices - sort of like a shoulder holster - only to carry the pump?

Second thought is a travel vest from either Filson or Scottevest both have many pockets to choose from, though I'm not sure how you'd manage the tube.

Cheapest solution might be my anti-pickpocket idea. Took an old pair of jeans and cut off all but the front pockets and the waistband. Wear it under the kilt. Let me hide my passport and real wallet while I kept a give away wallet in my sporran in case of mugging.

One of the jean pockets could hold the pump - if that's not too low on your body.