If the bike you are looking at is the one advertised on ebay, check it over carefully! From the photos, it looks as if it may be a 'new build' and possibly hasn't been run or road tested. Just from the photos, it will need other parts (rear chainguard and chain and twistgrip being the most obvious). Also, the front wheel is wrongly laced - all the spokes on the brakedrum side should be laced from the outside inwards - otherwise the spokes can foul on the brakeplate.
Regarding the dynamo - this should be quite easily obtained - again, ebay usually comes up trumps!
Hope this is of some help,