Walmart has many boys pajama sets on clearance, including many LEGO branded pajamas. Shipping is free w/ Walmart+ (90 day free trial here) or free on $35+ orders.
Social Edition Boys 2 Piece Long Sleeve Top and Long Pants Pajama Sleep Set with Matching Eye Mask, Sizes 4-16 $4.58 (a few options)
Social Edition Boys 2 Piece Illusion Layered Long Sleeve Top and Long Pants Pajama Sleep Set with Matching Eye Mask, Sizes 4-16 $4.74 (a couple options)
Sleep On It Boys Minky Fleece Pajama Set, 2-Piece, Sizes 6-14 $5.38 (several options)
Sleep On It Boys Hooded Minky Fleece Pajama Set, 2-Piece, Sizes 6-14 $5.38 (a couple options)
Lego Batman Boys Long Sleeve Tops and Long Pants, 4-Piece Pajama Sleep Set, Sizes 4-10 $8.00
Lego Baby Yoda Boys Long Sleeve Tops and Long Pants, 4-Piece Pajama Sleep Set, Sizes 4-10 $8.00
Lego Jurassic Boys Long Sleeve Tops and Long Pants, 4-Piece Pajama Sleep Set, Sizes 4-10 $8.00
Lego Ninjago Boys Long Sleeve Tops and Long Pants, 4-Piece Pajama Sleep Set, Sizes 4-10 $8.00
Lego Jurassic Boys Hooded Long Sleeve Top and Long Pants, 2-Piece Pajama Sleep Set, Sizes 4-12 $4.72
Lego Ninjago Boys Hooded Long Sleeve Top and Long Pants, 2-Piece Pajama Sleep Set, Sizes 4-12 $4.72
Pokemon Boys Fleece Pajama Set, 2-Piece, Sizes 4-10 $4.26
Star Wars Boys Fleece Pajama Set, 2-Piece, Sizes 4-10 $4.42
Nasa Boys 2 Pc Coat Pajama Set, Sizes 4-12 $4.58
NASA Boys 2 Pc Long Sleeve Long Pant Fleece Pajama Set, Sizes 4-12 $7.00
Nasa Boys 2-Piece Pajama Set, Sizes 4-12 $5.50
Batman Boys Fleece Pajama Set, 2-Piece, Sizes 4-10 $4.42
Batman Boys 2 Pc Long Sleeve Long Pant Fleece Pajama Set, Sizes 4-12 $4.74
Spider-Man Boys' Top and Shorts Pajama Set, 2-Piece, Sizes 4-10 $6.00
Social Edition Boys 2 Piece Long Sleeve Top and Long Pants Pajama Sleep Set with Matching Eye Mask, Sizes 4-16 $4.58 (a few options)
Social Edition Boys 2 Piece Illusion Layered Long Sleeve Top and Long Pants Pajama Sleep Set with Matching Eye Mask, Sizes 4-16 $4.74 (a couple options)
Sleep On It Boys Minky Fleece Pajama Set, 2-Piece, Sizes 6-14 $5.38 (several options)
Sleep On It Boys Hooded Minky Fleece Pajama Set, 2-Piece, Sizes 6-14 $5.38 (a couple options)
Lego Batman Boys Long Sleeve Tops and Long Pants, 4-Piece Pajama Sleep Set, Sizes 4-10 $8.00
Lego Baby Yoda Boys Long Sleeve Tops and Long Pants, 4-Piece Pajama Sleep Set, Sizes 4-10 $8.00
Lego Jurassic Boys Long Sleeve Tops and Long Pants, 4-Piece Pajama Sleep Set, Sizes 4-10 $8.00
Lego Ninjago Boys Long Sleeve Tops and Long Pants, 4-Piece Pajama Sleep Set, Sizes 4-10 $8.00
Lego Jurassic Boys Hooded Long Sleeve Top and Long Pants, 2-Piece Pajama Sleep Set, Sizes 4-12 $4.72
Lego Ninjago Boys Hooded Long Sleeve Top and Long Pants, 2-Piece Pajama Sleep Set, Sizes 4-12 $4.72
Pokemon Boys Fleece Pajama Set, 2-Piece, Sizes 4-10 $4.26
Star Wars Boys Fleece Pajama Set, 2-Piece, Sizes 4-10 $4.42
Nasa Boys 2 Pc Coat Pajama Set, Sizes 4-12 $4.58
NASA Boys 2 Pc Long Sleeve Long Pant Fleece Pajama Set, Sizes 4-12 $7.00
Nasa Boys 2-Piece Pajama Set, Sizes 4-12 $5.50
Batman Boys Fleece Pajama Set, 2-Piece, Sizes 4-10 $4.42
Batman Boys 2 Pc Long Sleeve Long Pant Fleece Pajama Set, Sizes 4-12 $4.74
Spider-Man Boys' Top and Shorts Pajama Set, 2-Piece, Sizes 4-10 $6.00