The "masthead light" and the "steaming light" are actually the same light located on the front of the mast about halfway up. There are no circumstances, motoring, sailing or anchoring, where that light is ever required to be used on a 26 ft sailboat if one has an all around white light at the top of the mast, a "mast top light" a.k.a. "anchor light."
To comply with the rules (without using a steaming/masthead light) including anchoring, motoring and sailing, you need:
(1) For motoring, a white 360 degree light at the top of the mast, plus red and green side lights,
(2) For sailing, a white stern light, plus red and green side lights. Alternatively, a three-colored light at the top of the mast.
(3) For anchoring, a white light at the top of the mast.
Thus, you have the option of just dispensing with the masthead light entirely. You can get a new regulation mast top light (anchor light) with an expected life of at least 10,000 hours burn time for less than $20 on Amazon, $40 at West Marine.
RULE 21 Definitions (a) “Masthead light” means a white light placed over the fore and aft centerline of the vessel showing an unbroken light over an arc of the horizon of 225 degrees and so fixed as to show the light from right ahead to 22.5 degrees abaft the beam on either side of the vessel.
RULE 23 Power-driven Vessels Underway (a) A power-driven vessel underway shall exhibit: (i) a masthead light forward; (ii) a second masthead light abaft of and higher than the forward one; except that a vessel of less than 50 meters in length shall not be obliged to exhibit such light but may do so; (iii) sidelights; and (iv) a sternlight.
RULE 23—CONTINUED (c) A power-driven vessel of less than 12 meters in length may, in lieu of the lights prescribed in paragraph (a) of this Rule, exhibit an all-round white light and sidelights.
RULE 25 Sailing Vessels Underway and Vessels Under Oars (a) A sailing vessel underway shall exhibit: (i) sidelights; (ii) a stern light. (b) In a sailing vessel of less than 20 meters in length the lights prescribed in paragraph (a) of this Rule may be combined in one lantern carried at or near the top of the mast where it can best be seen.
