ELEON Rhino Gland Nut Wrench - Set of 2 Adjustable Hydraulic Cylinder Pin Spanner Wrench - Heavy Duty Set Includes Gloves, Towel, Secure Pins - For Farm & Construction Equipment Nuts Under 7 Inches

It’s the accumulator on the brake master cylinder. Mine was doing it for years but not as frequent as yours is and it was still functional. I just replaced it last month. Toyota part number 47950-30010. You can find generic ones for about $150, I went with OEM and it was just north of $300. This https://a.co/d/03SarI2R is the tool I bought to remove the old one. Took all of 15 minutes to swap and now it’s nice and quiet.