As to some of the options available:
The most common low-cost option would be a maintenance work platform (sometimes called a maintenance cage) attached to the forks of the lift truck. Though I don't particularly like these, they are acceptable for occasional use and cost less than $1,000 (US).
Since it in sounds like you don't need to work all that high, a good rolling ladder is also an approved option. Once again, I don't particularly like rolling ladders but they are fine for occasional use.
There is also portable scaffolding that can be set up quickly for occasional use. I believe you can even get scaffolding with castors so you can roll it from one area to another.
In addition, there are numerous hydraulic work platforms that you simply roll to the location then either manually pump or use an electric pump to raise you to the proper level. These are safe and can be operated by one person (unlike a work platform attached to a lift truck).
Then you have scissors lifts that come in all types of configurations. If you only need it occasionally you can rent them from just about any equipment rental operation or purchase a used one at a reasonable price.