European duvet cover: Help with insert/blanket size?

[aristocatz]

I'm from the US & purchased a single duvet cover from Germany. I *think* it's a similar size to a twin in the US, but not exact.
The dimensions are 140 cm x 200 cm.

My questions:
1. What size duvet insert do I buy?
I've read some sites that say the insert should be a few inches smaller (ie 135x200) & other sites that say to get the exact same size
2. Any inexpensive sites to buy a European duvet insert? Everything I've come across is more expensive than what I paid for the cover!

Thank you for any input you might have!

 

[SirDuff]

Duvets where I live in Europe are sold as the same size as the covers (though where I live, to be special, we aren’t quite the same size as most of Europe), so that’s what I’d look for.

Sorry, not sure about the pricing of European sized duvets in the US. Maybe see how ‘off’ a twin or long-twin duvet is and if you can get away with using that?