The Lovehoney Main Squeeze range spring to mind, I find them super comfortable and a great price. Since yours are 45g you can skip the lightest ones and go for the intermediate (60g) or advanced (90g):
I used the Lelo Luna balls many moons ago but the string got really ick, I now prefer ones with a silicone 'string' so I can know they are clean. This set is a similar design to the Lelo one but with different weight combinations and a silicone string: