Do I Have to Have New Invisalign Retainer Made if I Need 2 New Crowns?

Since each crown is custom made, they will likely NOT be the same shape or size as your current teeth.  However, they MIGHT end up slightly smaller and can fit your current retainers.  The odds are slim, but exist.

I would plan on getting new retainers and hope for the best.

It seems like you are very happy with the final results after Invisalign!! Retainers get loose with time, and if you had treatment done i will strongly recommend you get new set of retainers. Go over with your dentist, if you need any other dental work done before you take impressions for the retainers. Also ask for types of retainers more affordable for you. You will keep your beautiful straight smile with new retainers.

Perhaps you should consider asking your dentist or orthodontist to bond an ortho wire behind the teeth on the lower to stabilize them in their position.  Its a small wire, precisely adapted to the surface of your lower teeth (on the tongue side) and then bonded into place.  This is done quite frequently at the end of treatment since patients so often lose their retainers/don't wear them etc.  Ask your dentist to make sure you are a candidate for this.  If you are, then you won't have to worry with making another Invisalign tray/retainer as this is a more permanent solution.