I used these and so far no leaks.
115 Buna-N O-Ring, 70A Durometer, Black, 11/16" ID, 7/8" OD, 3/32" Width (Pack of 100)
https://www.amazon.com/dp/B000FMWOQQ?psc=1&ref=ppx_yo2ov_dt_b_product_details
The pump is different on my 88 and takes a larger O ring easily available at the...