Not to speak for BigA, but I'd bet he'd recommend the synthelamin. You could probably check out the synthetek site or the sticky on this page. Good luck...
You can try syntheteks version or you could go to your local vet and buy it from there for about 10 bucks, though I know in some states you need a precription I doubt you will overseas! Though the only version I have tried is the b-12 in reforvit and that seemed to give me more energy than other forms of d-bol I know there are other things in it that could have attributed to it! In my state I saw it for 9 bucks but that was some time ago. It was 1000mcg/ml 10 ml bottle and I cannot remember the maker!
The reason I like Synthelamin is not just because it's double the strength of most others (2,000mcg/ml) but it's also stacked with different time release esters so you can just inj once a week if you want instead of the daily injections you have to do with normal B-12.
Generally, you can take one ml per week and you would get the same results as inj normal B12 once a day. But since it costs little (one bottle lasts you a year if you inj 2ml week) I use 1ml EOD or every few days, whenever I remember to take it.