Gift for my Mum - advice please

[Williams99]

Hi all, I'm looking for some advice on a potential watch purchase please.

Unfortunately we lost my Dad last week. He was always into his watches, and my Mum has mentioned she would like to do something with his watches to remember him by. Rather than selling his watches to buy something more suitable, I was considering getting her a watch as a gift from my brother and I. She can then keep his watches in their display case.

I have extremely limited watch knowledge, and was looking for advice on where/how to buy a watch and make sure I'm buying a proper one please. If anyone is keen to give me some advice, it would be greatly appreciated.

I know he had a Rolex or two, but his favourite watch was his Omega. Using a bit of Google reverse search, I'm pretty confident it was a Omega Seamaster Professional Diver 300m. I'll try and attach a photo but it's been a few years since I've Pistonheaded.

I believe I can get my Mum a smaller version of that same watch - in 28mm? Once again, I'm pretty confident my Dad's is the 41mm.

Specifically, I'm looking at this one on eBay, but even with the guarantees I'm wary of eBay.

https://ebay.io/m/xHOIXV

Is this a reasonable price for this watch? Anything specific to look out for? Or is there another retailer I should use first?

Thank you very much in advance for any advice. Please do correct me on anything and everything above, you can probably tell I'm out of my depth here!