Jason,
You didn't indicate whether you're diving with single tanks or doubles, or doing technical or recreational diving. Regardless, you have a number of options.
IMHO - In many, if not most, cases 'ditchable weight' is highly over-rated.
In technical diving you either have a physical overhead preventing direct access to the surface or you have a decompression obligation which imposes the same constraint. Surfacing to solve a problem could, under the right circumstances, kill you or put you in a wheelchair for the rest of your life. This is not a situation in which you want to dump a weightbelt at depth and thereby ensure you won't be able to maintain your decompression stops or controlled (slow) rate of ascent.
In very few cases while recreational diving do you find divers dumping their weightbelts AT DEPTH. (If I'm not mistaken, in the PADI program there is only one textbook entry regarding jettisoning a weightbelt, and its under 'finding an unconscious diver at depth and bringing them to the surface'. Moreover, in the course you learn that you ditch their weightbelt AFTER you arrive at the surface and stabilize them for surface tow or emergency breathing.)
A good recreational buddy team will work together to calmly deal with the problem, abort the dive and return safely to the surface - ditching weight and punching out is not generally step 1.
With a bp/wing and single tanks you have the options of backplates that weigh 6, 9, or 12 lbs; and weighted Single Tank Adapters (STAs) that can be provided in 4 and 6 lb weights, and in either one or two piece designs that add still additional flexibility in terms of weight. Some divers thread weights onto their waiststraps. The disadvantage is not that the weights are no longer ditchable, but that they are in the way of other things that belong on your waiststraps.
Divers who use double tanks (including small sets of double 63s or 72s - not all double sets are exclusively for technical divers) may choose either V-weights (fit between tanks and bp) or P-weights (fit inside the channel of the bp) of varying lbs of lead (in addition to heavier backplates as noted above). V-weights and P-weights (also known as channel weights) are also called trim weights. They are usually cast of lead, however, some companies offer 'soft' trim weights made of shot-filled neoprene. These look like ankle weights that have been fastened length-wise to the backplate (which still other divers have done!)
With only 4 lbs on your weightbelt, you haven't got a huge issue. No matter where you wear your weightbelt, 4 lbs is unlikely to be terribly uncomfortable. But if you want to avoid having the weightbelt as an issue, you do have other options.
