We have always noted in the past that it's not so easy to retrieve the values of Financial Dimensions or add a lookup of Financial Dimensions on to a form or dialog.
The following may be one of the easy ways to get that done.
To test this, we can create a quick form to display a few of the required lookup on financial dimensions as shown in the screenshot below:
You can modify this code to make it dynamics in nature instead of using constant values, this is just for the testing purpose.
Also, we need to create a new class which extends the SysLookup class and extend the lookupDimension method of the parent class as shown below: