Welcome aboard TF.
Here is a link to some swim ladder mods I made on my ladder.
It contains the original MS source info. If that's it or similar I have heard others have been successful getting parts. https://dkloeber.wixsite.com/bacchus/projects
Also The sticky at the top of the Marlow-Mainship forum has info re accessing part pics and source info for MS, Luhrs, Silverton & Hunter parts.
If that's not the one a pic or 2 would help.
The coating on my swim ladder is also degrading. Last week I removed any old loose coating, wire brushed the aluminum and applied white flex seal to those areas. We will see how long it holds up.
Part#: L0222200 (LADDER UNDRMNT 2-STP 18 WH)
Cost: $528.95 + UPS shipping
Lead Time: We will be able to ship this ladder the 2nd or 3rd Week of May
Terms: Visa or MasterCard