Here are some specs on Mares 1st stages:
15X DIN: 598 grams
15X INT: 772 grams
22X DIN: 685 grams
22X INT: 850 grams
52X DIN: 513 grams
52X INT: 687 grams
The weight difference between these 1st stages is fairly negligible, even for airline travel. All 3 above will perform relatively the same...the major difference is the layout of the ports. I recommend widening your search and go with whichever you can find that most fits your budget.
To better search, I recommend using the following iterations for each model listed above:
15X
Mares 15X
MR15
Mares MR15
MR is/was the Mares designation for their diaphragm type 1st stages.
You may find that among the 3 models listed above that the MR22 has higher availability on the used market as Mares has produced it for a very long time. It underwent a cosmetic redesign back around 2008. Here are pictures of the older version and the newer version for your situational awareness:
Older version:
View attachment 662465
Newer version:
View attachment 662466
-Z