I tend to buy monster high dolls and I've replaced the elastics before with the elastic ties that hold the dolls to the cards with varying success. I kinda hoard those plastic elastics though because I use them for everything around the house.
But my G3 elastics are showing wear as well. Some of the G3's had loops to work with and others had the elastics sewn right in. it might just be my humble opinion but I don't think the presence of the elastic makes much of a difference except when it comes to hats like Toboggans. I checked mine and she has the satin ribbon loops to slip the elastic through so you can likely easily loop something through it
I dunno if this helps you at all- I have friends who save their elastics for me when unboxing new dolls. they tend to be long and lanky and a great fit for replacing G3's elastics.