Mad prices on ebay for HTC Desire 310 batteries:
£90.68 Polarcell from Germany
£71.14 from Ireland

But more moderate:
Genuine HTC Desire 310 2000mAh Battery - 35H00221-00M - BA S960
£17.95

Ordered myself one from akku-land.de, using the original link.
With this result:
"many thanks for your order. Enclosed you will find our order confirmation.
Unfortunately, we must inform you that the goods you require are currently not available.
Please let us know if you are still interested in a shipment in week number 44 . "