4x40 Ro feed pump question

[Green mtn maple]

I picked up a 4x40 single post to with a pro on pump. No feed pump came with it. What would you suggest for a feed pump?
The membrane is new. Never had sap in it but ran well water. What should I do to rinse and preserve the membrane for the off season ?
I don’t have permeate to run through it.
Thank you in advance

[maple flats]

See if you can get 100+ gal of permeate from a local producer, they will have plenty now. If that fails get the softest water you can find to use, No chlorine! Check with the membrane manufacturer to see what preservative they use.

[Green mtn maple]

Thank you maple flats