Humidity in storage

I have a wine cooler that holds about 100 bottles. It has a temperature control but no humidification capability. I recently put a hygrometer inside the unit which registered about 42% humidity. I believe long-term storage should be in an atmosphere of 60% humidity. I have been putting moist paper towels in a bowl inside the cooler, but that only increased the reading to 44%.

Any suggestions as to how to significantly raise the humidity level and keep it there?

I'm beginning to think, Mike, that low humidity is not too much of a problem as long as the corks are kept in contact with the wine. Too much humidity, on the other hand can lead to mold and peeling labels. On that note, however, I have not seen a peeling label for years even on bottles stored in real wet conditions. I do not believe water soluble glues are used any longer.
I'll be interested in what others have to say.

I'm beginning to think, Mike, that low humidity is not too much of a problem as long as the corks are kept in contact with the wine. Too much humidity, on the other hand can lead to mold and peeling labels. On that note, however, I have not seen a peeling label for years even on bottles stored in real wet conditions. I do not believe water soluble glues are used any longer.
I'll be interested in what others have to say.

I have an old stone basement in my house. The labels on my '75 Lafite are moldy and deteriorating, but the corks are fine and have kept good levels - all still well into the neck. Looking at things from a different angle, as home winemaker, many of my friends save their empty wine bottles for me, so I have to clean off the labels and sterilize the bottles. Labels and glues vary all over the place. My technique is to put the bottles in my laundry tub, fill them with hot water, then fill the laundry tub with hot water. Some labels are simple paper, while others have a waterproof coating over them. Some of the waterproof glues soften in the presence of the hot water and label can simply be peeled off. Some labels do not have waterproof glue and after a short soak they fall off on their own. Then, some are exrtemely difficult to remove. These require scraping with a paint scraper, followed by rubbing with a paper towel soaked in mineral spirits.
Just as an aside, it seems that bottles from every country except Italy have the same standard neck diameter, designed to take a #9 cork. Italian wine bottles have a narrower neck, taking a #8 cork. #9s can be inserted into the Italian bottles, but it's much more difficult and they are also harder to pull out.

You may want to try the humidifiers that are used for cigar humidors. I did a quick google on cigar humidors and found a number of sources. Seemed fairly cheap but I am not sure how often you need to attend to them or how many it would take for a 100 bottle cooler.