try amazon.co.uk, I got mine 2nd hand through them.
That suprises me, that they are so expensive. Its a good book to own. Ebay is always a good place to look. Is there anything your particulaly interested in having a look at in the book?
For a M1 webbing sling try here http://www.ima-usa.com/product_info.php ... e08001113b I've used them before and I can recommend them 
As to M1 aeg performance they are all built from M14 base guns and as the changes are cosmetic the performance is the same as the base gun, because they are cheap a lot are based on AGM M14s, like mine, so look for reviews on them.
A lot of people on this forum have AGM M14s either in standard condition or converted to M1s and as far as I can tell they are reliable fairly accurate guns, try posting the question in the weapons thread you might get more response.
There is a lane opposite China Town ( in London), heading towards Carnaby Street. Sorry I can`t remember the name of the place, but it is about 100m from China Town.
The lane has a pile of collectors shops in it. One of these is a military and transport bookshop.
I bought my copy two months ago in that shop for the rec £29.99 It's a great book.
