I'd have to order it in order (ha) to know if it's available or not, STIHL doesn't take items back or they charge for it. I tried to cancel an order once and my dealer told me that wasn't possible, so I'll wait till you get a message back from the business you found. When I asked for your part I listed some other part numbers too and they told me the fleece air filter with part number 1124 120 1602 was still available, so if you need that too, look no further.
But another, much simpler option for you might be to just order another end cover for your carburetor. As far as I know, what that outlet on the bottom does is compensating for a dirty air filter. If you plan on keeping yours clean there is no reason why you shouldn't be able to use the closed version. The closed end cover for the HT-7A carburetor has part number 1124 121 0801