Chemical crosslinking will be able to keep the dimers from dissociating, but at the risk of interfering with the function of the protein. If you try this method, look for the lowest possible degree of crosslinking that achieves the desired effect.

You may be able to influence the stability of the dimers just by changing the buffer conditions, such as pH and salt.

I agree with Adam B Shapiro , chemical cross-linkers can covalently bond different subunits of a protein complex, enhancing stability.

However, the choice of cross-linker should be made carefully to avoid altering the protein's structure or function. The length and reactivity of the cross-linker are critical, as they determine the distance between subunits that can be linked without affecting the complex's native conformation. Also maintaining appropriate buffer conditions can significantly affect protein complex stability such as pH, ionic strength, co-factors & ligands. Furthermore, keeping the protein complex at lower temperatures can reduce thermal motion and help maintain the integrity of the complex. This is especially useful during purification and storage. Additionally, adding stabilizing agents like glycerol, sucrose, or certain salts can enhance protein stability by protecting against denaturation and aggregation.