I'm guessing that your daughter's coach wants you to buy a standard roll-up bag…..a "burrito" style bag, that will actually hold four pairs of skis in four zippered bags, and then rolls up, and straps closed. Most are made to hold skis up to 225cm, but you can fold the bag to shorten the overall size. They work just fine with a couple of pairs of skis, and my kids have used the big bag to fly with just SL skis. They fold over to accommodate shorter skis easily. Some companies make a shorter version, as well.
I've also found that it's a lot easier to get under 50lbs with this type of bag, BTW, if you're flying. A wheeled bag is heavier, and frankly when packing a van, storing them flat and unloaded, the burrito is easier to deal with. They last a long time. We still have a couple that are 15-20 years old. They've been dragged through airports all over the world. No issues.
Pretty much every race ski company has one branded for them. Generally the best pricing is through a rep, and at this time of year when skis are being ordered through clubs, academies and programs.
You can also search on line. Rossignol seems to build and sell a ton of these. I would check with Race Werks, Artech, The Race Place, Ski Depot, Reliable Racing…..the usual spots.
Here's one option, pretty classic bag, at a good price:
The SRD is a nice bag. They have sold the company and are rebranding it, so their old stock has been available at great prices.
Just my $.02