After you file

If you try to pay for Deluxe now, it will be at least 59.99

 

Since you haven't filed 2018,  you can downgrade it to Free Edition using "clear and start over", then upgrade to PLUS for 19.99.

I'll tell you all the steps if that's what you want to do.

 

There's also a free option if a return transcript will suit your purpose.   You may be able to immediately download one at the IRS website if you qualify to open an IRS account there.  Otherwise, to order a transcript to come by postal mail takes 5-10 calendar days.
http://www.irs.gov/Individuals/Get-Transcript