Is there such thing, which gives full power (~2,8A)?
Manafonts 1-mode supposedly gives only 2+A
http://www.manafont.com/product_info.php/generic-cree-t6-1mode-led-dropin-module-42v-max-p-5550
Any ideas about Solarforces own 1-mode dropin?
http://www.solarforce-sales.com/product_detail.php?t=RB&s=40&id=193
What about bare driver if not possible to get whole dropin as ready piece?
What are you considering as low voltage?
Are you looking to get full power from a couple of AA's?
What do you mean by low voltage? You want a driver only for a 18650?
Yes, Sorry I was not specific enough.
4,2V max.
I guess Nanjg 105 is what you are looking for, with a 2.8A on max. Yeah it can take higher voltage in, but it is very efficient on a 18650.
But it's not 1 mode. However it's several modes of your choice.
Piggyback two 1400ma AMC7135 circuit boards from KD. http://kaidomain.com/ProductDetails.aspx?ProductId=6653
Or double stack the the AMC7135 from one board to the other for a total of 8 AMC7135s . The above are one mode boards.