Since ammonia to urea is a conventional reversible reaction, it would be natural to assume the reverse as an option. In fact, there are patents for the Urea to ammonia process. Two of them, which are commercialized for the treatment of NOx, are U2A TM by EC&C Technologies and SafeDeNOx TM by 2002 Chemiton Enterprises, Inc., both with web sites in the internet.
However, none provides a solution for the separation of ammonia from CO2 in the gaseous phase or ammonium hydroxide from bicarbonate in the liquid aqueous phase. One is a straight water-phase reaction, the other uses steam and a catalyst. Both apparently proceed through the production of an intermediate: ammonium carbamate which is stable below 65 Celsius. Expensive metallurgies may be involved.
There is, however, another reaction using the enzime urease that selectively catalyses the hydrolysis of urea in water, not covered by patents, which I believe hasn't reached industrial applications. Again the separation of CO2 and NH3 has to be provided for.
It is still a strange market situation in which urea is cheaper than ammonia, since the normal production pattern is from ammonia to urea. Is the urea you plan to purchase diluted with water or does it have impurities ?
In short, I don't know of a better approach for your plans than consulting with the above companies besides doing some digging in the internet yourselves.