Use the want to sale section and caco forum. Think it need´s a vew weeks to find 4 l18, 175.4 and 5 K, And you go to 30-40% of your budget.
Same for cables, speakers, distroblocks and so on, all in the want to sale, very rare for the number of sells that ther is a hassle.
XS Power will get a powersale (10-20%) off in the end or beginning new year. Damn cheap prices in Europe you pay for a D 3100 650 $.
Or shoot a mail to RAM My link, he have ton´s of batt´s. Ask him he have another thread with other battsizes. And if you want order one or 2 extra
as reserve, or for a firend.