Yup, definately try to get him something larger. Glass tanks work great for gerbils, hamsters, mice, fish, and reptiles but I wouldn't recommend one for a rat. Right now since you have him in the glass tank just try to get him some out of the cage time. Drs. Foster and Smith has a very nice and big blue and white cage for $59.99 and an adequate green and white cage kit that comes with bedding, a wheel, and some other stuff for $52.99. If you don't want anything too expensive, go on petco.com and they have a tank topper for a 10 gallon tanks and it's $39.99. I had it for awhile for my girls and it worked great. I also agree with the others, try craigslist and freecycle!

Those two websites are:
http://petco.com/Content/HomePage.aspx?PC=home&Nav=1&=
and
http://www.drsfostersmith.com/default.cfm

Hope you can get him something bigger, and if you can't, please give him some out of the cage time! Hope I helped!