Water heater

Morning
 The original Cascade water heater in our 1997 Symphony was replaced by a Henry 10 years ago. That has now died too and I’m looking for a replacement. 
Can anyone suggest a replacement that fits the space?

I love our Symphony and want to keep it going as long as possible, so any help would be very welcome.

Cascades were good, here's one on ebay...
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Thanks Ian
 That’s really kind of you to send the link, but I forgot to say that we need a gas and electric one. I have looked on eBay but didn’t see anything second hand.

I've just found 2 gas/electric on ebay, here's one.....

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Here's the other....

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Thank you Paul
That’s really helpful. I’m a novice at looking for old parts. 
I didn’t think of looking for Carvers, only Henrys. The first one looks very good and I’ll bid for it. Fingers crossed.