I have listed for sale a lens cap for the meade ETX 90 - but it should fit any 90mm telescope! This lens cap is 3D printed from TPU, a hard wearing and flexible filament to slip securely over the lens. I have printed this lens cap in a natty translucent purple to perfectly match the OTA on the ETX 90 Observer series, and also because it's the colour I have! So if your ETX is midnight blue then this will add a little colour. Anyway, if you have misplaced your original lens cap then you need one of these, very reasonably priced at £3.50 plus postage and plus whatever eBay add on.
eBay