A/C Evaporator Coil Leaking

My 1600sqft house currently has a 3 ton Lennox system with heat pump. It stopped blowing cold air and A/C tech have identified a leak in the evaporator coil as the culprit. The system is around 6 years old and out of warranty.

I'm hearing that due to supply issues, replacement coils cannot be had currently. And with no estimation on when stock will be available, my only option is to purchase a new air handler. Awaiting exact numbers but was told ballpark for replacement handler installed is 4k.

Anyone in the A/C business or has had a recent similar experience care to chime in? Seems a bit high to me but the contractor was knowledgeable and seems like he will do quality work. Also, is it a bad idea to mix brands on equipment? I'd hate to get another Lennox, given how soon this unit failed.

TIA