Im a Morris Minor restorer at heart and apart from the location of the securing lug and hole they are simelar. Options are, any engineering place should easily knock one up for you, model lathe person or small fabricator, whoever you know!!
second, try an auto one (like morris minor!!) just that it doesnt have the lug for securing thru the chassis
BUT it does have a small lug underneath (on your flat section opposite side to the TEE) with a hole in for a 10mm sized bolt!!! Still `looks` the samish and secures thru a small hole (or original with a spacer or couple washers each side!) Bit of paint on the washers and hard to tell difference if you looking for authenticity!!
Look here iis just one example from a specialist
http://www.morrisminorspares.net/shop_item.php?ID=1471