For sailmaking, you need "spurtooth grommets", which have teeth to engage in the cloth. I have standardised on number 2, which have a finished inside diameter of 12mm. For lashing purposes, this is quite big enough. 

Rather than buy from the USA, you might look at Kayospruce in the UK, where number 2 brass spurtooth grommets are £20 per hundred.

I am thinking of making a split junk rig.  I worried about matching the vertical dimensions of the jiblets to the rest of the sail, when it occurred to me that I can make the jiblets adjustable if I put an eyelet in each corner and tie each jiblet to the battens.  So I looked at the tools on sailrite.com.  They sell 7/8" brass rings for $5.20.  I can find the same size brass rings for $1.20 each on eBay.  Is there any difference between brass rings for leather work and those Sailrite sells that justifies over four times the cost?