Here is my finished waist padding:
The waist band can also be flipped up so that the padding faces your waist for a smaller baby.
Here is what this project cost me:
Infantino Mei Tai carrier: $15
2 pieces of Girasol wrap scrap: $30 and $20
1" high density foam: $2
purple thread: $2
Here is a screenshot of a custom mei tai for sale on a B/S/T page: Just examples of wrap conversions so you can see my inspiration. Mine is not that fancy but I think I saved some money trying to make my own and mine may be a bit more comfortable with the waist padding.