We are using a bassinet that was made about 10 years ago. We took measurements for the mattress pad and it's coming up as a custom size (17.5 x 36). We have found many 18 x 36 online, but none in store to see if they would fit. Anyone have any prior experience with this? I'd gate to order one and it not fit, but would also hate to custom order one if we don't need to!

My SIL says she just went to the store and picked one up and didn't need a custom size (they used it for their children).