I’m not here to go all in but I’m on the beginning of my fitness journey but I discussed training schedules with my fysiotherapist and he recommends low intensity cardio for building up stamina.
I do prefer HIIT because of the rush it gives me and at my level it won’t make a big difference but low intensity cardio is your baseline.
https://enduranceengineer.com/aerobic-base-building-for-endurance/
Perhaps the seller doesn’t ship overseas? I’m Belgian and I’ve got that with US shops sometimes.