I would try the Analytics - DataSet to see if it's also an issue in that context. If you know just a little bit of SuiteScript, the thing could be resolved in a function of probably under 10 lines.
Another idea: custom field on the record that is a non-stored field, type integer, that has as its default value LENGTH({thereallylongfield}). Then search on that field. EDITED TO ADD: Ugh ... I don't think you can search on a non-stored field. Well, make it a stored field, set the value using MASS UPDATE or CSV Import (or scripting), and then you can search on it.