There are quite a few On-line sellers, it's just a matter of price and how fast and accurately they can get the parts to you.
I quit using several online sellers because they would mess up my order and end up sending me the wrong parts, one seller sent the wrong part three times on the same order!

A lot of discount sellers will not order the part from Kubota till you order it from them thus causing a week plus delay in even getting your parts to them and then they forward it on to you.
Some local dealers do a great job at getting there customers parts for good prices, and if they get it shipped as part of there regular order then they normally don't charge you any shipping.