If your into true BB'ing you may find that you really do not need heavy DL's for your goals. Assuming heavy, lower rep DL'ing produced serious muscle mass for everyone can be misleading. Most guy's have crap style anyway (check out some of the DL'ing vid's shown by GB members), which only invites injury as more weight is used. I also assume that gym does not have heavier DB's (150 & up) where you might DL that way. Heavy DB's are an excellent way to improve the overall starting power of the DL. Just to add, if doing one arm DL's for a while, the strength may closely match your regular two hand version rather quickly. The grip will vastly improve.
Seems as how you may be stuck at that gym, than make the most of a bad experience and try for higher rep Dl'ing per set. As 15 to 20 reps. Might surprise you as to affect these can have on muscle size & strength. Be advised that most men avoid higher rep compound exercises because "it's too much like work". Which, I guess, is the whole point of working out in the first place. Also throw in some GM'ing and bent over rows for more strength to the lower back (also outstanding lat's).
When you do join a more serious gym, your Dl'ing basic structure should be well geared for heavier lower rep work, if that is your main concern. Good Luck.
Side Bar: If allowed, you could tie two DB's, on each side, inside the collars for added leverage.
